The present invention relates to an apparatus for turning over a sheet on which an image is formed by means of am image forming apparatus, such as a duplicating machine and a printer, and also relates to a sheet orientation apparatus for piling successive sheets in a desired order.
In an image forming apparatus such as an electrophotographic copying machine, there is sometimes provided a sheet turn-over apparatus in order to form images on both sides of a sheet or pile successive sheets in a correct order.
In order to attain the former function, after an image has been formed on one side of a sheet and the sheet has been turned over, at a suitable timing the sheet is supplied again into a toner image transfer position. Therefore, the apparatus is liable to be large is size and complicated in construction. In the latter application, since the apparatus is sufficient to have the function of merely turning over a sheet, a rather simple and small apparatus has been proposed. But there are only few practical apparatuses. For instance, in Japanese patent application Laid-open Publication No. 50,943/74, there is disclosed a sheet turn over apparatus in which a sheet moving horizontally is fed upwardly and then the rear edge is clamped between feed rollers and the sheet is fed horizontally. In this known apparatus, since the sheet is fed completely in an upright manner, the sheet is liable to be bent and thus the turn over might not be effected correctly. Particularly, when the sheet is thin, it might be jammed.
In Japanese patent application Laid-open Publication No. 97,744/77 there is further proposed a sheet turn over apparatus in which a horizontally moving sheet is fed upwardly along an inclined sheet guide and then the sheet is fed horizontally in a reverse direction.
FIG. 1 is a cross section illustrating the known sheet turn over apparatus disclosed in Japanese patent application Laid-open Publication No. 97,744/77. The reference numeral 1 denotes a main body, 2 and 3 first and second rollers for feeding a sheet horizontally, 4 guide plates for guiding the sheet into a nip portion between the first and second rollers 2 and 3, a sheet support plate 5 for receiving a sheet 6 fed out of the main body 1 on its inclined surface, and the reference numeral 7 represents a sheet stop member which is rotatably journaled about a shaft 8 and can take, selectively, a first position shown in the drawing and a second position shifted by 90.degree. with respect to the first position viewed in the counterclockwise direction. Reference numerals 9 and 10 denote third and fourth rollers, arranged vertically underneath the second roller 3. The reference numeral 11 represents a guide plate for reversing the sheet substantially through 180.degree., and reference numeral 12 denotes a sheet discharged on a sheet tray 13.
When the sheet stop member 7 is in the first position shown in FIG. 1, after the sheet 6 has been completely fed leftward along the sheet support plate 5 by means of the first and second rollers 2 and 3, the rear edge of sheet 6 falls down due to the gravitational force and is clamped into a nip portion between the second and third rollers 3 and 9 as illustrated in FIG. 1. Then the sheet 6 is fed by the second and third rollers 3 and 9 and passes along the guide plate 11. After that the sheet is fed into the nip portion between the third and fourth rollers 9 and 10 and is fed horizontally leftward. In this manner, the sheet is turned over and is discharged onto the sheet tray 13.
On the other hand, when the sheet stop member 7 is in the second position, after a sheet has been clamped and fed between the first and second rollers 2 and 3 onto the sheet support member 5, it is prevented by the sheet stop member 7 from falling down into the nip portion between the second and third rollers 3 and 9. In this manner successive sheets are discharged on the sheet support member 5 which now serves as a sheet tray.
FIG. 2 is a front view showing the outer appearance of a known copying machine the desk top type. A reference numeral 14 denotes a main body, 15 and 16 denote discharging rollers and a reference numeral 17 represents a sheet tray. Usually the discharging rollers 15 and 16 are arranged near the bottom of main body 14 and the sheet tray 17 is arranged horizontally or substantially horizontally so as to receive stably a sheet fed out of the main body 14 by means of the discharging rollers 15 and 16. In FIG. 2, reference numeral 18 denotes a sheet supply tray. In the case of applying the known sheet turn over apparatus shown in FIG. 1 to the copying machine illustrated in FIG. 2, the following disadvantages will be encountered.
In the apparatus illustrated in FIG. 1, the third and fourth rollers 9 and 10 which function to turn over the sheet are aligned vertically with respect to the first and second rollers 2 and 3, and thus there is required a relatively large space below the rollers 2 and 3. Thus the whole apparatus is liable to be large. Further, since the traveling direction of the sheet has to be changed substantially over 180.degree. along the third roller 9 by means of the guide member 11, it is necessary to make the diameter of the third roller 9 sufficiently large, otherwise the sheet would not be curved smoothly and might be jammed frequently.
Moreover, in the case of providing the ability for selecting a first mode in which a sheet is discharged without being turned over and a second mode in which a sheet is turned over, in the known apparatus shown in FIG. 1, it is impossible to discharge sheets on the same tray. Further, in the first mode, since the sheet support member 5 serving as the sheet tray is inclined by a very large angle, a number of sheets could not be supported stably and further it is rather difficult to take out a stack of sheets. Moreover, in the case of applying the sheet turn over apparatus shown in FIG. 1 to a copying apparatus in which a toner image is fixed onto a sheet by heating it, since a sheet discharged onto the inclined sheet support member 5 is still hot or at least warm, when a sheet, particularly a thin sheet, is bent or curved, the sheet is permanently deformed after being cooled.
Further, in the case of adopting the known sheet turn over apparatus shown in FIG. 1 to the general copying machine illustrated in FIG. 2 as an optional apparatus, it is necessary to arrange the sheet turning over rollers 9 and 10 immediately below the sheet discharging rollers 2 and 3 arranged in the main body 1, and therefore, there results a problem that construction and handling of a detaching mechanism might be complicated.
In an image forming apparatus such as a duplicating machine and a printer, an image record sheet is discharged on a tray while a recorded surface is faces upward, and the next sheet is piled on the last sheet. Therefore, if a plurality of originals arranged in a normal order of pages are duplicated, recorded sheets are stacked on the tray in a reversed order of pages.
In Japanese patent application Laid-open Publication No. 37,433/77, there is proposed a collating apparatus in which successive recorded sheets are turned over and then are discharged on the tray. However, in such a known apparatus, since the turned over sheets are always discharged on the tray, a user could not confirm the condition of images recorded on the sheets. Such a drawback also occurs in case of using the sheet turn over apparatus disclosed in the above mentioned Japanese patent application Laid-open Publication No. 97,744/77.
Further, known collating apparatuses which have been used in practice have in addition to the collating function a so-called sorting function in which a plurality of sets of successive sheets are discharged on separate trays. However such apparatuses are very complicated in construction and quite large in size.